I am in my 60s, had a right-side mx with node clearance end of May. Just finished chemo and starting rads next week. You don't say if you have had any reconstruction done or if you have to have chemo and such like. I understand what you mean about the fixed smile, my OH has his own health problems and I don't want to worry him unnecessarily, so like you, I keep the smile there most of the time, not always easy as you know. Physically I haven't had many problems with the mx or chemo, emotionally good days, bad days but can usually hold back the tears until OH has gone to bed (he's not good with tears). You don't say when your last surgery was but if you are still having pain after 2 or 3 weeks, you should speak to your BCN.
There is a thread for more mature post-menopausal women, I will find it and bump for you to have a read through, it may be of some help.